WO1998007800A2

WO1998007800A2 - Method of adhesively assembling cellulosic products

Info

Publication number: WO1998007800A2
Application number: PCT/US1997/013736
Authority: WO
Inventors: David L. Remerowski; Duane C. Shomler; Anthony T. Racca; David J. Lococo
Original assignee: Senco Products, Inc.
Priority date: 1996-08-05
Filing date: 1997-08-04
Publication date: 1998-02-26
Also published as: US5985082A; WO1998007800A3; AU3827797A

Abstract

A clean, neat and effective method for adhesively assembling cellulosic products entails placing adjacent to the surfaces to be joined a device which comprises: a target element contiguous with a heat activatable adhesive material, said target element being absorbent of electromagnetic waves which are convertible to heat energy to activate said adhesive material, holding said surfaces together, and exposing said device to electromagnetic waves to produce heat sufficient to activate the adhesive material and effect a bonded relationship between the assembled cellulosic pieces.

Description

METHOD OF ADHESIVELY ASSEMBLING CELLULOSIC PRODUCTS

CROSS REFERENCE TO A RELATED APPLICATION This application relates to U.S. Patent Application Serial No. filed on even date herewith and entitled "Adhesive Device" by Shomler et al. Said application and its

disclosure are hereby incorporated by reference.

BACKGROUND OF THE INVENTION This disclosure relates to the assembly of a variety of cellulosic products using an adhesive device that is activated by electromagnetic waves. The cellulosic products

include assemblies such as corrugated boxes, cartons, other paper packaging, books, and articles being fashioned from fabric materials such as cotton, linen and the like.

Examples of manufactured items that have cellulosic materials attached to them are bed frames and box springs, office and commercial seating, upholstered chairs and sofas,

auto, airplane, boat and bus upholstery and headliners, lambrequins, drapery and curtain assemblies, awnings, outdoor furniture, clothing, shoes and the like. The adhesive assembly of cellulosic products is typically effected by stitching and employing a variety of adhesives. However, these traditional fastening means are rapidly falling into disfavor as it becomes desirable and even necessary to work quicker and neater and form even more secure adhesive bonds. It is apparent, then, that inventions are waiting to be made which address the placement of adhesive material in a neat, clean,

safe and effective manner especially with regard to the assembly of cellulosic products. Not surprisingly then, others have experimented with alternatives to traditional fastening devices for adhesively joining the components of an assembled product. Description of the Prior Art: United States Patent 4,038,120 to Russell describes the use of an energized heating element or wire to heat a hot melt glue resulting in adhesion

between contiguously assembled panels. The reference method involves heating a glue-coated wire to liquefy the glue producing a cohesive state and facilitating the assembly of panels. This method is particularly useful for introducing a cohesive material (glue) to an area of limited accessibility (groove), but the heating element (wire)

requires the direct application of energy (electricity) to provide the heat to melt glue.

United States Patent 3,574,031 to Heller et al. describes a method and material for welding thermoplastic bodies by using a susceptor between the bodies to be joined. The

susceptor sealant is characterized by having particles, heatable by induction, dielectric or radiant energy, dispersed in a thermoplastic carrier compatible with the thermoplastic sheets to be welded. The welding of the thermoplastic sheets is effected by exposing the susceptor sealant to heat energy, softening the carrier material and joining all thermoplastic materials. United States Patent 3,996,402 to Sindt relates to the assembly of sheet materials by the use of a fastening device utilizing an apertured sheet of eddy current-conducting material sandwiched between coatings of hot-melt glue. An induction heating system is activated causing eddy current heating in the EC-conducting material with consequent

melting of the hot-melt glue thus resulting in fusion and, ultimately, bonding of the sheet materials in accordance with the desired construction. SUMMARY OF THE INVENTION

The presently disclosed method of adhesively adhering component pieces of an assembled cellulosic product is distinguished from, and improves upon, the prior art by utilizing a device to be placed adjacent to the surfaces to be joined which comprises a target element contiguous with a heat activatable adhesive material said target element

being absorbent of electromagnetic waves which are convertible to heat energy for activating the adhesive material, holding said surfaces together, and exposing said device to electromagnetic waves to produce heat sufficient to activate the adhesive material to effect an adhesive bond between the component pieces of the assembled cellulosic

product.

DESCRIPTION OF THE PREFERRED EMBODIMENT

It is imperative that the assembly of simple cellulosic products be constructed as efficiently as possible. There is not a lot of technology or know-how in the fabrication of these items. Typically, they're made of bulk quantities of rolled paper and bolts of fabric fastened by stitching or traditional glues, adhesives and hot melts. The bulk rolled or bolt materials are cut to the required dimensions before assembly. In some cases this step

is done by different manufacturers with the precut pieces or components being shipped from a mill or manufacturer to a manufacturer who specializes in assembly of the finished product. The disclosed method could allow the cellulosic components to arrive at the assembly point with the adhesive device already in place. It is believed that the

disclosed method of assembling cellulosic products will provide definite advantages of cost safety and appearance over traditionally fastened cellulosic products. By the term "cellulosic products" is meant all cloth and paper products having cellulose polymers as a fundamental structural unit and capable of being fabricated into a variety of forms and shapes so as to perform the innumerable functions observed and envisioned for these versatile materials. Also, bear in mind that these cellulosic products are characteristically made in assembly line operations. They're made with standard pieces according to standard specifications. This uniformity of composition and process is well suited for the employment of an adhesive device that can be desirably situated between or adjacent to pieces to be joined in the assembly of a product and activated to adhesively join the components into a sturdy, well -constructed product.

Looking at the adhesive device employed in the disclosed method in greater detail, we see that the target element must, for the most part, be fashioned from materials or substances that are not transparent to electromagnetic waves. Indeed, the target element will necessarily be constructed of a composition that will absorb electromagnetic waves. Once absorbed by the target element, these waves will produce magnetic hysteresis and eddy currents resulting in heat energy which will melt or activate the contiguous adhesive material.

Typically, the target element will be fashioned from metallic materials such as

steel, aluminum, copper, nickel or amalgams thereof which have proven utility and are readily available; although, some semi-metallic materials such as carbon and silicon are also known to be suitable for the absorption of electromagnetic waves.

The target element can assume any form or shape consistent with the overall configuration of the adhesive device. Frequently, the target element will be presented as a metallic foil, mesh or strip, and, in some instances, it will be more effective to present

the target element in the form of a fiber, chip or flake of an electromagnetic absorbable material. The point to be made is that the target element need only be fashioned from a material reasonably impervious to, and absorptive of, electromagnetic waves.

In use, the adhesive device needs to be situated adjacent to the pieces or components of the cellulosic product to be assembled. As a practical matter, of course, all cellulosic products are transparent to electromagnetic waves. Some cellulosic materials will be more transparent than others, and empirical adjustments can and will be made to modulate the quantity and intensity of electromagnetic wave energy needed to optimally activate the adhesive material.

In many instances, it will be sufficient for the adhesive device simply to be placed adjacent to the cellulosic pieces to be assembled. In other construction or

assembly situations, it will be necessary to make some arrangements or take additional steps to make sure the adhesive device remains in place prior to activation. Such an additional step need be little more than introducing an attachment element such as a small pressure sensitive adhesive area on the surface of the device . Simpler means for positioning the device prior to activation might include clamping, tacking, stapling or spiking to make sure the adhesive device is situated and activated in the most effective and, therefore, most desirable location. But these measures, of course, would be optional procedures and in no way essential to the performance of the device in its broadest typical

and routine applications. When desirably situated adjacent to the cellulosic components of the product to be assembled, the adhesive device is ready to be exposed to electromagnetic waves , produced by and emanating from a generator powered by a source of alternating electric

current. The generator can be held in a fixed position for assembly-line production or designed to be manipulated so as to quickly and easily pass over, around or near the strategically "hidden" device while emitting electromagnetic waves which will penetrate the "transparent" cellulosic components to be assembled, be absorbed by the target element, be converted to heat energy, activate the adhesive material resulting in a bonded relationship between the pieces of the cellulosic product to be assembled. To elaborate, somewhat, heat is produced in the conductive target element by two mechanisms: eddy current resistive heating and magnetic hysteresis. Eddy current resistive heating applies to all conductive materials and is produced in the target element by the electromagnetic waves emanating from the generator. The heat resulting from magnetic hysteresis is observed only in magnetic materials. As the electromagnetic field

produced by the generator reverses polarity, the magnetized atoms or molecules in the target element also reverse. There is an energy loss in this reversal which is analogous to friction: This energy loss is magnetic hysteresis. The "lost" energy is quickly converted to heat and conducted by the target material to the contiguous, and frequently enveloping,

heat-activatable adhesive material to initiate adhesion. When heated to the necessary temperature, the adhesive material will liquefy or become heat-activated, attach itself to the surfaces to be joined and, on cooling, create an adhesive relationship between the joined cellulosic components of the assembled product..

Two adhesion mechanisms, hot-melt and heat-activated cure, are proposed for use with the disclosed device. Both mechanisms are initiated by heat emanating from the target element. Hot-melt adhesives are solid at ambient temperatures, but melt or liquefy

when the temperature is elevated by, for instance, heat accumulating in the target element. The melted adhesive "wets" the adherends and attaches to the surface of the pieces to be bonded. As the adhesive cools, the adherends and adhesive are bonded by the electrostatic attraction of polar molecular groups. Note that for the hot-melt

mechanism, the bonding is reversible. Thus by repeating the induction heating procedure, the bond can be undone and the adherends separated. The ability to reverse the adhesion and separate adhesively assembled pieces is not a trivial attribute. In addition to the obvious advantage of being able to reassemble or repair misaligned pieces

in assembled products, it may also be desirable to be able to disassemble adhesively assembled products to facilitate serviceability and repair. Heat-activated curing adhesives are also solid and easy to manipulate at ambient temperatures, but when the adhesive temperature is elevated by, for example, the heat

emanating from the target element, a chemical reaction is initiated. This reaction involves a cure or crosslinked bonding either within the adhesive or between the adherends. Such bonds are typically irreversible. Frequently, a heat-activated curing adhesive bond will demonstrate an electrostatic attraction between the adhesive and the

adherends and a crosslinked bond within itself.

While the foregoing is a complete description of the disclosed method, numerous variations and modifications may also be employed to implement the purpose of the invention. And, therefore, the elaboration provided should not be assumed to limit the scope of the invention which is intended to be defined by the appended claims.

Claims

What is claimed is:

1. A method of assembling cellulosic products which comprises placing adjacent to the surfaces to be joined a device which comprises: a target element contiguous with a heat activatable adhesive material, said target material being absorbent of electromagnetic

waves which are convertible to heat energy to activate said adhesive material, holding said surfaces together, and exposing said device to electromagnetic waves to produce heat sufficient to activate the adhesive material to effect a bonded relationship between the component pieces.

2. An assembled cellulosic product including an adhesive device which comprises: a target element contiguous with a heat activatable adhesive material, said target material being absorbent of electromagnetic waves which are convertible to heat energy to activate said adhesive material.